This invention relates to a disc cartridge, and more particularly to a disc cartridge having a disc-like medium such as a recordable/reproducible optical disc, a magneto-optical disc or the like rotatably received in a casing.
In general, an information medium including, for example, a disc medium such as a magnetic disc, an optical disc, a magneto-optical disc or the like is used in the form of a disc cartridge while being received in a casing formed by joining upper and lower casing members to each other. The disc cartridge includes a shutter for opening and closing openings such as head insertion holes, drive shaft insertion holes and the like formed at of the upper and lower casing members of the casing. For such a conventional disc cartridge, a shutter operation system is proposed as disclosed in Japanese Patent Application Laid-Open Publication No. 226046/1995, wherein a shutter which is made of metal is fixed on a slider by means of screws, so that sliding movement of the slider on a casing permits the shutter to be slidably guided on the casing. Also, a number of systems for opening a shutter in both lateral directions of a casing are proposed for a disc cartridge which has a both-sided recordable/reproducible disc-like medium received in the casing. For example, Japanese Patent Application Laid-Open Publication No. 153221/1995 or No. 43279/1985 discloses a shutter operation system wherein a slidetype shutter is provided on both sides thereof with return springs such as coiled torsion springs for urging the shutter in a closing direction to close head insertion holes and the like in a manner to be independent from each other.
The former shutter operation system described above fails to small-size the disc cartridge because it causes a distance between an end of the slider and the shutter opposite thereto to be disadvantageously increased. Also, a structure of the slider employed in the system fails to apply the slider to a disc cartridge of the double-direction sliding type that the shutter is open in both lateral directions. Further, fixing of the shutter on the slider by means of the screws in the former system causes both the number of parts for the disc cartridge and the number of steps for assembling of the disc cartridge to be increased. Also, it leads to a variation in direction of the assembling, resulting in the assembling being substantially troublesome.
The latter shutter operation system of the double-direction sliding type wherein the shutter is opened in both lateral directions of the casing causes a portion of the shutter engaged with a shutter operation member of a recording/reproducing apparatus to be formed with a groove-like configuration. Such configuration of the shutter gives rise to application of load to the shutter, leading to damage to the shutter such as deformation thereof, breakage thereof or the like, because operation of the shutter is carried out by abutment of the shutter operation member against the shutter relatively reduced in thickness. Also, the latter system is complicated in manufacturing to a degree sufficient to cause an increase in cost of the disc cartridge. Further, it causes a deterioration in easiness of assembling of the shutter. More particularly, assembling of the shutter and return springs with respect to the upper and lower casing members of the casing is highly troublesome and difficult, to thereby deteriorate mass-production of the disc cartridge. For example, when incorporation of the return springs in any one of the upper and lower casing members is carried out prior to joining between the upper casing member and the lower casing, holding of the springs on the slider is failed to cause the springs to be disengaged from the casing member due to an elastic force of the springs, resulting in automation of the assembling and energy savings in the assembling being substantially failed. Incorporation of the return springs after the joining eliminates such a disadvantage as described above. However, it requires to form a side surface of a front portion of the casing with a large opening for inserting the springs therethrough into the casing. Unfortunately, this causes dust or the like to enter the casing through the opening. Also, it causes the slider and the like to be exposed through the opening, leading to damage thereto, so that the disc cartridge is deteriorated in durability. In addition, it fails in small-sizing of the disc cartridge and fails to permit the disc cartridge to exhibit easiness in assembling and reliability in operation.
Furthermore, in the case that the head insertion holes are each formed with a width reduced as compared with a width of the casing defined in a direction of movement of the shutter, a space is formed between an end of the shutter in an opening direction to open the head insertion holes and an end of the casing when the shutter is open, so that the coiled torsion springs do not cause any problem. However, in the case that the end of the shutter approaches the end of the casing when the shutter is open, deformation of the coiled torsion springs is increased to a degree sufficient to deteriorate durability of the springs. Also, this causes a space in which a coil portion of each of the coiled torsion springs is moved to be lost. Thus, it is required to reduce a size of the coil portion. However, this leads to a deterioration in durability of the spring.
Moreover, the double-direction sliding shutter structure has a further disadvantage that it is required to pay attention to production of shavings due to operation of the slider and an error of dimensions of the slider. Otherwise, satisfactory operation of the shutter is failed.
It is generally known in the art that the conventional disc cartridge is provided with an erasure prevention member in a manner to be movable, so that a user may select any one of "recordable" and "unrecordable" states when the record medium is received in the casing. Also, it is known that detection of "recordable" or "unrecordable" is carried out depending on light transmission through the casing or mechanical on-off operation of a switch. When the record medium or disc received in the casing of the disc cartridge is of the double-sided recordable/reproducible type, it is required to arrange the erasure prevention member for each of both sides. For example, Japanese Utility Model Publication No. 41189/1986 proposes a disc cartridge which is so constructed that a casing is provided on a side surface thereof with holes through which two erasure prevention members each provided on each of upper and lower surfaces thereof with a projection are operated, respectively.
However, the above-described arrangement of two such erasure prevention members requires any identification means because the disc cartridge fails to clarify correspondence between the two erasure prevention members and both upper and lower surfaces of the disc. Also, the above-described configuration of the erasure prevention members causes interference between the members and the casing during assembling of the disc cartridge, to thereby render the assembling highly troublesome, because the assembling is generally carried out by incorporating parts of the disc cartridge in one of the upper and lower casing members of the casing and then joining the other casing member to the one casing member.